In recent years, mobile communication systems represented by such communication systems as GSM system, PCS system, PDC system and CDMA system (so-called mobile phone) have spread worldwide.
In general, the mobile communication system of this type is made up of an antenna which emits and receives radio waves, a radio-frequency power amplifier (RF power module) which amplifies a power-modulated radio-frequency signal and supplies the amplified signal to the antenna, a receiver which processes the radio-frequency signal received by the antenna, a control unit which controls these components and a battery which supplies power supply voltage to these components.
Japanese Patent Application Laid-Open Publication No. 2008-42038 (Patent Document 1) describes a technique in which a semiconductor chip in which an LDMOSFET making up a power amplifier circuit of an RF power module is formed is flip-chip mounted on an upper surface of a wiring board.
Japanese Patent Application Laid-Open Publication No. 2003-273520 (Patent Document 2) describes a technique relating to a via of a PA stacked module.
Japanese Patent Application Laid-Open Publication No. 2001-244274 (Patent Document 3) describes a technique for improving the reliability of a semiconductor device by reducing the pressure applied to an electrode of an HBT when mounting a semiconductor chip having the HBT formed therein on a wiring board and also by surely contacting a lead-out electrode and a package base substrate (wiring board).
Concretely, an emitter lead-out electrode which commonly connects the emitter electrodes of a plurality of HBTs is formed. Further, a dent is provided in a region of the emitter lead-out electrode located on each emitter electrode. By this means, in the flip-chip mounting in which the emitter lead-out electrode is contacted to the package base substrate, the application of the bonding pressure to the emitter electrode is prevented by the dent.